Method of making cast iron



Oct. 3, 1939. M. KuNlANsKY METHOD OF MAKING CASTv IRON Original Filed July 2, 1934 lllllllulld llllllll ||||L Patented Oct. 3, 1939 Nl'rso STATES rArs'Nr oir-Fics 2,174,519 METHOD oF Mame `o'as'r mon Max Kuniansky, Lynchburg, va.-

11 Claims.

apparent only upon continued use. More often,

15 photomicrographs of the cast iron indicated that the structural arrangement of the compounds and elements in the product was such as to in.-Iz

herently result in undesirable qualities of the material.

forming iron castings, dilculty is encountered in obtaining the proper content of carbon and other desirable compoundsV and elements.

In general, I employ a material which is laching in those compounds or elements which are desired inthe final product. For instance, I may employ a steel scrap which is low in, say,' carbon,

and which will not ordinarily produce a desirable cast iron. I may employ also a malleable iron or mixture of malleable iron and steel scrap. More over, with either the malleable iron or steel, I may mix cast iron. It may be stated that I aim to employ materials `which are low in content of the desirable compounds or elements.

Starting with this basic material, I subject the scrap or the mixtures, as set forth, to a melting and remelting operation in contact with carbon, and I have found that it is generally desirable to add a graphitizing agent preferably while the step. l

The melting and remelting operation is preferably conducted in cupola furnaces where the material is in contact with the furnace coke and absorbs carbon to raise the carbon content.

` It is an object of my invention to producer a good quality cast iron in the process of which I may employ scrap material.

Anotherobject of my invention is to produce a good quality of cast iron economically and with simple and well known apparatus, in a process in which the control factors are' easily regulated.

Referring to the drawing, I have shown diagrammatically the sequence of steps which I may 55 employ in the preferred forms of my process. It

Where cast iron was not used asthe basis for material is in the molten state in the remeltlng (Cl. 'Z5-130) is to be understood that the diagrammatic illustration is not limiting, and that any one or more of the features of my process. either alone or in combination with other features, may be protected, if novel. Therefore, I wish to have my 5 invention limited inits scope solely by the appended claims of this application and by the showing of the prior art.

In the drawing:

The-single figure of the drawing diagrammati- 10 cally illustrates some preferred embodiments of the process which I employ.

In the manufacture oi cast iron according to my process, I may employ a lmaterial.'which is lacking in desired nal constituents. Preferably l5v I employ a material which is largely steel scrap,

and which lacks the requisite high carbon content for cast iron. I may employ a malleable cast iron melt which also is lov.r in carbon content in comparison to the requisite carbon con- 2 tent of the nal cast iron product. Mixtures of material may be employed, such for instance as a mixture of steel scrap and malleable or wrought iron. In fact, I may employ a mixture, for instance, of steel scrap and cast iron.

By employing as a starting material a substance which lacks the requisite high percentage of some of the elements or compounds in the nal product, I am enabled to carefully control the amount of such elements or compounds which 30 may be added. Moreover, I have found that a very uniform nely grained cast iron can be obtained by my process. The gray iron which can be made by my process has high twistability, is

tough, can be made of varying degrees of ma- 851 chinability. sistant.

Some of the characteristics of the iron made by my process are predictable from photomicrographs of the material. Other characteristics 40 which distinguish it from ordinary cast iron of either the gray or white variety are not detectable through a study of the photomicrographs, but appear readily under tests, such as hardness, twistability, abrasive tests, and so forth.

I prefer to employ cupola furnaces for melting the material, and I have found that by melting the material in a cupola furnace considerable economies can be effected over, for instance, a treatment in an electric furnace in contact with carbon. The cupola furnace treatment, while economical, also supplies the requisite carbon addition,.which is desirable.

The starting material, which, as I have stated, may be steel scrap, malleable cast iron, or any The WhiteY` iron is very wear-reof low sulphur content or it may be ordinary coke of somewhat lower carbon and higher sulphur content. Sometimes it is possible to eliminate the desulphurizing step which may be employed after the initial melting, if a high carbonlow sulphur coke ,is employed. 'Ihe higher the carbon content of the coke employed, the.greater will be the addition of carbon to the iron in thisv initial melt. Therefore, if it is desirable to have an 'ironv of relatively high carbon content as a iinal product, one of the ways of insuring this desirable high carbon content is to use a high carbon coke in the rst melt. The coke should have such a high contentof carbon that it will carbonize the melt to a considerable extent.

The melted material runs down into the forehearth of the furnace, where a soda ash desulphurization treatment may be employed, if it is desirable. Other desulphurizing agents than soda ash can be used, and I am not to be limited to .this particular treatment. A compound or mixture comprising lsodium carbonate or other suitable material is mixed with the molten material in the'- forehearth and the sulphur content of the melt is largely reduced.

'I'he material is then run into ingots, and the ingots are cast. These ingots are broken upI and The second charged to a second cupola furnace. cupola furnace may contain a high carbon coke with low sulphur content, or ordinary coke, and here again the desired characteristics of the final product determine the type of coke employed. If

a very high carbon iron is desired, high carbon coke is employed. Moreover, if the sulphur content of the coke is low, the use of the sodaash or desulphurizing step may be eliminated. It is 'to be understood, however, that even .where a high carbon-low sulphur coke is employed in either the rst or the second melt, it may be desirable in my process, after the first melt or after the second melt, or after both melts, to employ a soda ash y desulphurizing and purifying treatment.`

In my process, therefore, I may pass the second melt to the forehearth of the furnaceand desulphurize it with a soda ash or some other desulthe-remelt cupola, a graphitizing agent should be added. As a graphitizing agent I usually employ some of the zirconium alloys. Such alloys may contain a considerable amount of iron and other materials, and I preferably employ alloys which contain a considerable amount of iron in their composition, although this is not a necessity.

The alloys which I add to produce the graphitizing have a number of dierent compositions. It

' is not always necessary to use a zirconium alloy.

For instance, I may employ an iron-silicon alloy in which I use iron and 75% silicon. Anotherv alloy which I may employ has the following .com-

position: I

Per cent Fe Zr 15 Mn 10 Si 4o ariannaA I can also employ calcium and silicon alloys, or calcium and titanium alloys. 'I'he calcium and titanium perform a function somewhat analogous to that of the zirconium, and though I have mentioned calcium silicide and titanium silicide as possible alloys that may be used, it must be realized that I can employ'alloys embodying calcium or titanium which are more complex. Other alloys which maybe used have approximately the following compositions:

Iron-silicon-zirconium Per cent Zr 12-14 S1 40-42 Fe 41-42 Silicon-zirconium f Per cent Zr 36-38 SL 50-52 Fe 8-12 C .25

zirconium-manganese-silicon Per cent Zr J 20-24 Mn 10-12 Si 58-62 Fev 8-12 Al- .75 C .03

Whether lor not I add the material in the remelt cupola or in the forehearth of the remelt cupola, or in the ladle which is filled from tapping the forehearth of the remelt cupola, is a matter of choice, depending upon the desirable characteristics of the final product and the nature of the initial charge.

In general, I employ as a base material about 85-100% steel scrap, the remainder being scrap iron. The amount of alloy which I add to the remelt material 1s from about 1% te 3% by weight of the molten material. In some instances I may exceed 3%, but ordinarily this is not desirable.

- I find that there is great homogeneity in gray iron castings made from my iron. Photomicrographsvshow that there is relatively small differ` .ence'between thestructure of thin castings and thickcastings. This desirable feature of my inaterial distinguishes it from the usual gray iron.

Though I have to date been unable to show from photomicrographs any easily discernible difference between my white iron and ordinary white iron, I do find that the resistance to abrasion or,

iron, is nevertheless an important distinguishing feature of my white iron and one which makes it of peculiar utility 'in uses where high resistance to abrasion is desirable, such as in the piping of abrasive materials.

As a-variation of `my process, I may add the `graphitizing agent during or after the first melt and before remelting in any of the alternate forms of the process disclosed herein. Again, I may add the graphitizing agent both before the casting of -the ingots and during the remelt step, or in the forehearth of the remelt cupola, or in the ladle from the remelt step.

Referring to the single s heet of the drawing, I have diagrammatically illustrated the process. The charge is placed in a cupola furnace l and is melted, and ows to a forehearth 2. From the forehearth 2 the molten material is cast into ingots indicated at 3. 'Ihe ingots are broken up, as indicated in the step 4.

The ingots when broken up are charged to a second cupola furnace 5, and the molten material runs to a forehearth 6. From the forehearth 6 the molten material is tapped into a ladle 1.

TheV molten material inthe first forehearth may be subjected to an optional desulphurization step. Likewise, the molten material in the forehearth 6 may be desulphurized. If necessary, desulphurization ofthe material in both the forehearth 2 and the forehearth 6 may be carried out. If the molten material is low in sulphur, the desulphurizing step after the melting operation of each cupola can be dispensed with. A graphitizing agent can be added in the cupola of the first furnace or in the forehearth of the rst furnace. Some of the graphitizing agent may be placed in the cupola with the charge, and some of the graphitizing agent may be added in the forehearth 2.

The ,addition of graphitizing agent may be postponed until the second melting, in which case the graphitizing alloy may be added to the second cupola furnace or the graphitizing alloy can be placed in the melt in the forehearth 6 of the second cupola furnace, or the graphitizing agent can be added in the ladle "l. As a variation of the process, the graphitizing ag'ent can be added at 'all of the places indicated by the dotted arrows in the single figure of the drawing, or in some of the places. The amount of graphitizing agent added, and the place or places of addition vare matters which are determined by the operating characteristics o the apparatus, the type of coke used in the cupola furnace, the type of initial material, and the desired characteristics of the iinal products What has just been said in connection with the graphitizing agent is also true of the desulphurization steps. Desulphurizing at either or both of the places indicated on the drawing is to be controlled by the type of material treated, the characteristics of the coke used in the cupola furnaces, the time of operation, the proportions of coke and ingredients, and the desired characteristics of the final product. In fact, graphitizing and desulphurizing depend on the various complex factors of operation which can be determined by one skilled in the art. The graphitizing must occur at some one or more points in the process. The desulphurizing may be entirely dispensed with under certain conditions.

It is desired that I be limited solely by the appended claims and the showingQ of the prior art.

I claim:

1. A method of making cast iron comprising melting a mixture of cast iron and malleable cast iron in a cupola furnace where carbon is picked up by the molten mass. casting this melt into ingots, remelting the ingots in a second cupola where additional carbon is picked up by the molten mass, and adding a graphitizing agent.

2. A method of making cast iron comprising subjecting a mixture of cast iron and malleable cast iron tp a melting operation in contact with carbon where carbon is picked up by the molten mass, casting this melt into ingots, remelting again in contact with carbon where additional carbon is picked up by the molten mass, and

adding a. graphitizing agent in a quantity not over three percent by weight.

3. A process of making cast iron comprising melting and remelting a mixture of cast iron and malleable cast iron in a cupola furnace in both of which melting operations carbon is added to the molten mass, and adding a graphitizing agent in the forehearth of the cupola furnace.

4. A process of making cast iron comprising subjecting a mixture of cast iron and a malleable cast iron to a melting step in a cupola furnace in contact with high carbon coke, casting Athis melt and remelting the castings in a second cupola in contact with a high carbon coke in both of which melting operations carbon is added to the molten mass.

5. A method of making cast iron comprising melting a mixture of cast iron and a malleable cast iron in contact with carbon where carbon is picked up by the molten mass, desulphurizing the melt, solidifying the molten material, remelting the solid material in contact with carbon where additional carbon is picked up by the molten mass, and desulphurizing the second melt.

6. A process of making cast iron comprising melting and remelting a mixture of cast iron and a malleable cast iron in both of which melting operations Vcarbon is added to the molten mass, and adding a graphitizing agent before the remelt.

7. The method of making a low phosphorus gray cast iron which consists in melting down a mixture of cast iron and a malleable cast iron in a cupola, casting the molten metal into ingots, remelting the ingots in a cupola to add carbon, adding to the molten metal an alloy of iron, manganese, zirconium. and silicon. the alloy forming not over three percent by weight of the molten metal, and casting the metal 'mto molds.

8. The method of making a. low phosphorus gray cast iron which consists in melting down a mixture of cast iron.anda malleable castniron in a cupola, casting the molten metal into ingots. remelting the ingots in a cupola to add carbon, adding to the molten metal a graphitizing agent not over three percent by Weight, and casting the metal into molds.

9. The method of making a low phosphorusgray cast iron which consists in melting down a mixture of cast iron and a malleable cast iron in a, cupola, casting the molten metal into ingots, remelting the ingots in a. cupola to add carbon, and adding to the molten metal one percent to three percent of an alloy made up substantially as follows: iron 35%, zirconium` 15%, manganese and silicon 40%.

10. The method of making a low phosphorus gray cast iron which consists in melting down a mixture of cast iron and a malleable cast iron in a cupola, casting the molten metal into ingots, remelting the ingots in a cupola to add carbon, adding to the metal an alloy of iron, manganese, zirconium and silicon, the alloy forming not over 3 per cent by weight of the metal, and casting the metal into molds.

11. The method of making a low phosphorus gray cast iron which consists in melting down a mixture of cast iron and a malleable cast iron in a cupola, casting the molten metal into ingots,

Vremelting the ingots in a cupola to add carbon,

and adding to the molten metal an alloy of iron,

manganese,` zirconium and silicon, the alloy forming not over 3 per cent by weight of the metal.

MAX KUNIANSKY. 

